On a 2008 Mercedes-Benz E550, the owner’s manual calls for 85W-90 hypoid gear oil to be used in the rear differential on a car. However, there are very few suppliers of 85W-90 hypoid gear oil, one of them LiquiMoly and another one is buying OEM fluids from the dealership.
I don’t want to run LiquiMoly gear oil for reasons that you’ve shared with us. And, it is likely that LiquiMoly supplies Mercedes-Benz with the same gear oil used in OEM packaging (though I haven’t checked).
Do you think it would be okay to use Valvoline 80W-90 High Performance Hypoid gear oil, ranked #5 on your gear oil/transmission oil testing list, inside that rear differential?
Thank you for your help in advance,
Sam
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Hi Sam,
Valvoline 80W-90 High Performance, “conventional” GL-5 hypoid extreme pressure gear oil would be a good choice for conventional differentials. But, it is “NOT” for limited slip differentials.
Valvoline 75W-90 Full “Synthetic”, GL-5 hypoid extreme pressure gear oil is a good choice for conventional “OR” limited slip differentials.
So, choose between either one of these as needed for your vehicle, and you will good to go.
Hello Mr. Rat,
Public service announcement with regards to hybrid and plug in hybrid. The extra money you pay up front may be offset by gas savings ( only if the majority of driving is “city” ) but then all those break even savings are lost when you have to fix/replace the battery and other associated repairs due to its complexity.
Dean
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Hi Dean,
Was wondering (after f3’ing my brains out) if you have plans to ever test Amsoil Signature Series 0W-40 Synthetic Motor Oil?
Thanks for reading and have a good day
~Paul
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Hi again Paul,
No, because a multi-viscosity 40wt motor oil is THICKER than ideal for most water-cooled, gasoline engine applications.
And a multi-viscosity 20wt motor oil is THINNER than ideal for most most water-cooled, gasoline engine applications.
But, a multi-viscosity 30wt motor oil is THE IDEAL viscosity for most most water-cooled, gasoline engine applications.
Since it is just not possible to test every last motor oil on the market, I focus mostly on multi-viscosity 30wt motor oils, that have the highest value, for the most people.
However, the Amsoil Signature Series line of oil, is very good. So, for your particular application, you could run 0W40 Amsoil Signature Series with no concern at all, even if I have not tested it.
If I owned your particular High Horsepower WRX STi, with its marginal bottom end design, I would use 0W40 Amsoil Signature Series, so that I could sleep better at night.
Your car is an exception where a multi-viscosity 30wt motor oil is NOT the best choice. You will kick yourself if you blow your engine up from running the wrong viscosity motor oil, when you have been made aware of the viscosity that is the BEST choice for you to be running.
People doing the right thing, don’t blow-up their engine. That’s why I recommended you use 0W40 Amsoil Signature Series. Because it is the BEST choice for your particular application, and will provide a higher “Margin of Safety”, as we call it in Engineering.
As I have said before, for most cases, here is how a motor oil should be chosen, in this exact order:
1. Select the correct viscosity.
2. Select a highly ranked, high psi oil from my Wear Protection Ranking List.
However, for any questions about special cases, get in touch with me here.
I make Engineering recommendations based on each specific application I am asked about. But of course, each reader ultimately has to decide for themselves, what they want to do with that recommendation.
First off, thanks for this work you’ve committed yourself to for years now. I’ve been following it for about 4 years on and off.
So let me get to it: I own a VW.
The 5w30 QSFS isn’t euro rated for VW. I did find a QSFS 5w40 euro that rates pretty well on your testing but I wanted to ask how important is the Euro tag on the bottle?
Can I run the QSFS 5w30?
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Hi David,
Thanks for being one of my many Blog followers.
If your VW has a Diesel engine, then you should use a “Euro” motor oil.
If your VW has a gasoline engine, then 5W30 QSFS (Quaker State Full Synthetic), API SP, would be the BEST choice.
So as cheesy as it might sound and based on what I can hear, see, as well as my butt dyno / ass sensor inputs are telling me, the Amsoil 0W40 signature series seems to be a great match for my build/motor. It actually smoothed out the idle a small amount, enough to notice! Power feels more linear and pushes sooner in the lower RPM range.
I also went and put in Amsoil 75W90 severe gear oil and even that made a difference in the sense that the drive train noise quieted down and smoothed out as well, including a smoother shift through the gears!!
Crazy! Well thought I’d share….back to lurk mode
Thanks for reading.
-Paul
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Hi again Paul,
Hopefully, you will be lurking again soon to read my response here.
Two things, one GOOD, and one BAD:
1. GOOD – I’m glad to see that you are very happy with the 0W40 Amsoil Signature Series oil that I recommended specifically for your build/motor.
2. BAD – You obviously have not read my Tech Article #55 on Gear Oil Tests.
If you had, you would know that 75W90 Amsoil Severe Gear Oil was THE WORST performing gear oil I tested. It is ranked 11th out of the 11 Gear Oils I tested. It is one of Amsoil’s WORST performing products.
My strong recommendation is for this gear oil to NEVER be used. One of my other Blog readers reported that he and his buddies were getting a lot of metal particles on their differential magnetic drain plugs when using this gear oil. When they changed to a better gear oil from my Gear Oil Test, the metal particles disappeared.
NOTE: The HIGHER the psi value, the BETTER the Wear Protection. Here are the comparison numbers:
75W90 Amsoil Severe Gear Oil = ONLY 78,481 psi
75W-90 Valvoline Full Synthetic Gear Oil = 121,502 psi
So as you can see, the 75W-90 Valvoline Full Synthetic Gear Oil provides a WHOPPING 55% MORE WEAR PROTECTION than that pathetic 75W90 Amsoil Severe Gear Oil.
I did see that section, but I had impulse ordered that and was about to return it for the 75W110 version but decided to run this for a short period as like a flush to get the Motul out.
I saw some good News today. Now GM says they are not abandoning their gas V-8 engines after all, to switch to all electric vehicles only. That really surprised me because GM’s CEO has prided herself in being a radical climate fanatic. I guess she finally got a clue that GM would collapse if they only offer electric vehicles. Your thoughts?
Zenyatta
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Hi again,
Yes, I saw that in the News also. And that did come as a total surprise. Because GM’s utterly worthless and completely incompetent CEO Mary Barra, has for a long time been saying “matter of factly” that GM was converting to an All-EV Company by 2030 or 2035, depending on which News article you read. And absolutely no exceptions were ever mentioned.
Now today, she back-pedaled and GM announced that they are NOT going to abandon their gas engines. They said they will still offer gas V-8’s in their full-size pick-ups, SUV’s, and larger trucks. And they said they are investing nearly a $billion dollars in 4 new factories to produce those engines.
Making such an abrupt reversal in their future plans, would make you think that much smarter people than her at GM, could see they were heading toward the cliff of extinction, perhaps from Market Research.
Because it is quite clear that Americans simply do NOT want EV’s which are THE WORST vehicles ever created. They are miserable to live with, and many EV buyers are suffering massive buyer’s remorse.
Especially as more and more buyers discover that in freezing weather, EV’s are simply unworkable because of 50% reductions in driving range and EXTREME DIFFICULTIES in recharging. One owner of a new very expensive Hummer EV, found out that the largest home charger you can buy, took 5 DAYS, yes 5 DAYS to fully recharge his Hummer. He had major buyer’s remorse.
So, you have to wonder if GM’s Board of Directors told CEO Mary Barra to make some serious changes if she wanted to keep her job.
Whatever the case, that is a major move in the right direction for GM. And with Ford already planning separate Gas and Electric Divisions, now it will be interesting to see if Chrysler revises their All-Electric plans, now that they are the only major American Automaker claiming to be switching to all EV’s. TBD…
Good Morning.
Very Interesting Blog. I appreciate the view. Interesting on the PSI and not so much on the traditional ZDDP and or truck oil.
I have seen this blog many times. I have read through it.
I have had failures in the past, and I have had good results. I dont want to name oils here.
so…to my questions…or I am soliciting a recommendation from you…
I am running a 427 cubic inch Ford windsor engine(stroked 351) with a dart block and eagle steel crank-rods. I run a solid roller cam with pressure fed solid roller lifters. Makes an Honest 680hp on the dyno. 12 to 1 compression. I run high octane gas–110
To date, I have run rotella 15/40w dino and mobil 1 15/50 synthetic. No reliability issues to date, low use, under 20 hrs. Maybe 10-20 runs at the drag strip. To date, the rotella was faster than the mobil 1 15/50….
I want a lighter oil. I want a reliable oil. I see your list.
I have been told the Mobil1 0w40 is a good hearty oil..its a Heavy 30wt not really a full 40wt), I see it on your list. I also see the mobil 1 racing 5w30 on your list…(shocked at your rating -psi).
Would you care to recommend an oil?
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Hi Harry,
As you are probably aware, roller motors are not finicky about what oil they use, like flat tappet motors are. So, roller motors can use many different oils without any major issue.
But, the fact that you are here asking for a recommendation, indicates you would like to run an excellent motor oil that will provide the best wear protection for your engine.
You came to the right place for CORRECT/FACTUAL Engineering information that is backed-up by hard Engineering Test Data. I am the ONLY one anywhere, who backs-up everything I post with hard data, proving everything I say.
You will only find reliable and accurate information right here in my Engineering Blog. I started my Blog 10 years ago so that Car Guys would FINALLY have some place to go for TRUE information.
And I have numerous Blog reader testimonials in the body of my Blog, PROVING that my Engineering Test Data EXACTLY MATCHES real world experience.
The notions that High Performance engines need High ZDDP and/or Heavy Duty Diesel oils, are pure nonsense. They are only MYTHS that were just “made-up” by unqualified and incompetent people. And now they are perpetuated on Automotive Forums and elsewhere, by people who have no idea what they are talking about. But of course, repeating BAD/WRONG information a million times, does NOT make it magically become true.
Anything you read or are told about motor oil that is not backed-up by hard Engineering Test Data, is only opinion, theory, speculation, or guessing.
The fact is, Engineering Test Data has PROVEN over and over again, that Heavy Duty Diesel oils produce low psi numbers, and they reach the onset of thermal breakdown sooner than the better, far superior gas engine oils.
Also, experience and Engineering Test Data, have shown time and time again, that High ZDDP motor oils, including Break-In oils, typically produce very low psi numbers, and actually are very likely to CAUSE wear, damage and failure. That’s why flat tappet engines keep wiping lobes when they use High ZDDP oils.
ZDDP is just an old, outdated, obsolete anti-wear component from the last century. It has been FAR SURPASSED by modern, proprietary, 21st century anti-wear formulations. That’s why many new API SP motor oils are SO MUCH BETTER than old style high ZDDP oils. Hotrodders and Racers need to get with the program and switch to the newer oils, if they want the best protection for their engines.
When it comes to the TRUTH about motor oil wear protection capability, the ONLY thing that matters, is the psi value an oil can produce in my Engineering Torture Test on motor oil. The HIGHER the psi value, the BETTER the wear protection capability.
*****
You did not say what sort of engine clearances you are running, nor if you are running a standard volume oil pump, or a high volume oil pump. Both of those have a great impact on the “HOT” oil pressure your engine is capable of generating.
The old rule of thumb for High Performance and Racing engines, is that they should produce “at least” 10 psi of “HOT” oil pressure at normal operating temperature, for every 1,000 rpm. For example, you want to see “at least” 40 psi of “HOT” oil pressure at 4,000 rpm, etc, etc.
My number 1, All-Time BEST, Record Setting psi motor oil, which produces THE BEST Wear Protection Capability ever recorded, is modern 5W30 Quaker State Full Synthetic (QSFS), API SP. And you can even get great prices on it at Walmart.
I use 5W30 QSFS in ALL of my own engines, including old school flat tappet, modern stock and High Performance, big cubic inch, and Supercharged.
I have numerous Drag Racer readers who use that 5W30 QSFS oil in their old school flat tappet race engines, with GREAT success.
So, “IF” your engine can generate acceptable “HOT” oil pressure with a 5W30 motor oil, that oil is your answer for a lighter, reliable oil.
With all other things being equal, the thinner/lighter the motor oil, the quicker your car will be at the Drag Strip, because of less viscous drag, which frees more HP to move the car.
However, if your engine requires a thicker oil to maintain acceptable “ HOT” oil pressure, then I recommend using 0W40 Amsoil Signature Series motor oil.
Just to clarify, I found 2 types of packaging for the Valvoline gear oil. So wanted to ask which is the one you tested? Please and thanks.
1. Valvoline FlexFill Full Synthetic 75W-90
2. Valvoline SynPower 75W-90
Thanks much and talk soon
~Paul
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Hi again Paul,
I tested Valvoline FlexFill Full Synthetic 75W-90. That is the one you want. Just so you know, “FlexFill” is only a reference to the container the gear oil comes in, which often makes it more convenient to put in the vehicle. But, the gear oil itself is called “Valvoline Full Synthetic 75W-90”.
Valvoline SynPower 75W-90 is an older gear oil Valvoline no longer produces, and is no longer shown on their website. Though there is likely a lot of it still in warehouses.
And they have dropped the “SynPower” name, which is no longer on their current products.
Hello 540Rat.
I looked at Mobil 1’s website and at their product data sheet and saw that their 15w50 is now API SP rated as well the FS 0w40and FS 5w40 . I talked to a rep at Mobil 1 to confirm and he said “this is correct.” I was wondering if you would be testing any of those for air-cooled equipment? Thanks again! – Joe
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Hi Joe,
Here we go again. That Mobil 1, 15W50 was the source of some uncomfortable discussions here a few months ago, regarding whether or not it was really API SP.
At that time, I could not find anywhere on their website showing that it was really API SP. And I could not find an API SP version in person either.
But, one of my readers insisted it was API SP. He even sent a picture of it showing API SP. So, the whole thing was a total mess. And I said I would not touch that Frankenstein oil with a 10 foot pole.
Now, I just looked at TWO different Mobil 1 links, and AGAIN, including their product data sheet, neither one showed it as API SP. Apparently Mobil 1 is incompetent. They can’t even get their website right.
I don’t know what you are looking at on-line that shows it as API SP. But, if it is that hard to find, I would not trust it.
If I ever come across Mobil 1, 15W50 in person that has API SP on the bottle, I “might” get one to test.
But, I’m not as much of a fan of Mobil 1 oils, as some of my readers are. Because their performance is very inconsistent on psi value, and their performance at higher temperatures can be rather poor as well.
I never use Mobil 1 oils myself, and I never recommend their oils either. So, I would have to decide if testing a newer version of their 15W50 is worth my time, effort, and money.
Plus, I lost all respect for the Mobil 1 Brand when they came out with their extremely poor performing 5W30 Annual Protection oil, which is ranked a pathetic 178th out of 286 motor oils tested so far. That oil is a TOTAL scam from a dishonest Company, that is only intended to separate gullible people from their money.
And their prior/current Mobil 1, 15W50 is horrible, with a value of only 70,235 psi, which ranks it a miserable 237th out of 286 oils tested so far. So, I wouldn’t hold my breath for a newer version to be WAY better.
There are plenty of other oils, and some are quite good, to choose from in my Tech Article on Air-Cooled Engine Oils. So, no one “needs” another Mobil 1 oil.
XW40 oils are NOT thick enough to be acceptable choices for air-cooled engines.
Only XW50 and XW60 oils are truly suitable for air-cooled engines.
You can NEVER trust anything a Company Rep ever says. They are every bit as bad as a Used Car Salesmen.
Hello Mr. Rat,
I was Canadian Tire today looking for deals on oil and the only one on sale was the Mobil 1 annual protection. I initially thought it should be at least as good as their other stuff because its Mobil synthetic – and then the rational part of my brain kicked in and said don’t buy it unless I see some psi numbers! Glad I happened upon this QandA.
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Hi Dean,
The is “no guarantee” that a Mobil 1 Synthetic motor oil will automatically be a good oil. There are a good number of Mobil 1 Synthetic motor oils that are poor performers that are not worth using.
For some reason, people tend to think all Mobil 1 oils are great. But, that is simply NOT true. All anyone has to do is read through my whole Wear Protection Ranking List.
Then they can see for themselves, that some Mobil 1 oils perform well, and some Mobil 1 oils perform poorly. But, you cannot know which is which until you look through my Ranking List.
Mobil 1 Annual Protection was “On Sale” for one reason. It is because that overly expensive, poor performing oil, was discontinued after one year because of poor sales.
So now, places that have it in stock, are still trying to dump their old stock of it by putting it “On Sale” just to get rid of it.
You did the right thing by avoiding it. Because it is not worth using even if it was free. A massive 177 other motor oils on my Ranking List perform BETTER than that oil.
Motul 75w90 is out of stock just about everywhere. Those that do have it in stock want ridiculous $$$ per quart.
Is there an alternative gear oil you would recommend since the Motul is unobtanium?
Thanks again for all your hard work!
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Hi again,
I’m not sure why you would think that Motul Gear Oil is “The Gear Oil” to use. Because there is “nothing” special about Motul. It is NOT the Best performing Brand. Motul is just another “ordinary” Brand.
But, I suspect Automotive Forum people say Motul is the greatest Brand out there. However, Automotive Forums only throw out Bad/Wrong information. Because the unqualified people there have no idea what they are talking about. Automotive Forums are THE WORST places to ever go for information.
I started my Engineering Blog 10 years ago, so that Car Guys would FINALLY have a place to go for the “Truth”.
Not only do I have an alternative to Motul Gear Oil for you, I have a “Significantly Superior” Gear Oil for you.
In my Engineering Torture Test on Lubricating Oils, these two Gear Oils produced:
Motul 75W90 Gear 300 Fluid = 103,868 psi
Valvoline 75W-90 Full Synthetic Gear Oil = 121,502 psi, which provides 17% BETTER WEAR PROTECTION than the Motul 75W90.
NOTE: The HIGHER the psi value, the BETTER the Wear Protection Capability.
So, if you use Valvoline 75W-90 Full Synthetic Gear Oil, you will be MUCH BETTER OFF, than if you used the Motul you originally had in mind.
Thought you’d be interested in my oil report on the Coyote with the first fill of QSFS 5w30 – by comparison, *significantly* less iron and less overall other wear metals than the previous test which ran Pennzoil Platinum 5w30. That was also during harder working conditions for the engine (cold, short runs etc.)
Once again, the regional(?) Costco Kirkland Signature 5w30 oil is on sale (among their other offerings, including a diesel oil) and i was reminded that other, lesser testing than you perform, showed it to be a pretty reasonable oil, especially for the price, then remembered you didn’t have a test of it 😀
The recent gear oil discussions reminded me that i needed to order some more Valvoline 75w90 for the front diff as it’s due a change, i do like the Flexfill containers, they were really convenient on the Amsoil 75w140.
Take care
Maxx,
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Hi again Maxx,
No, I have not tested Costco/Kirkland labeled 5W30 motor oil because their Management refused to sell me single quart to test. And I was not about to buy a case of low priced, low quality motor oil, just to test one quart, then dump the whole rest of the case. So, I will never test that oil.
Do NOT be gullible enough to believe that any “lesser” testing on motor oil has any value at all.
I spent a LOT of time, a LOT of effort, and a LOT of money, drawing from my years as a Professional Mechanical Engineer and Car Guy, to develop my proprietary Engineering Test Protocol on motor oil, that EXACTLY matches real world experience.
NO ONE ELSE ANYWHERE, has access to my Engineering Test Protocol. Because it is my own Intellectual Property that will never be shared. So, my Engineering Test Data is the ONLY Test Data that is accurate and reliable.
Thanks for sharing the info on your 5W30 QSFS (Quaker State Full Synthetic, for those not familiar with the abbreviation) used oil Lab Test report.
That is yet another validation of the accuracy of my Engineering Torture Test on motor oil, which shows 5W30 QSFS to provide THE BEST wear protection on the market today.
It is ranked “NUMBER 1”, producing an amazing 152,674 psi, which is the HIGHEST/BEST value ever recorded for wear protection capability, out of a whopping 286 motor oils tested so far.
EVERY Race, traditional flat tappet, Supercharged, Turbocharged, European, and Motorcycle, water-cooled, gas engine that can use 5W30, is BEST served and BEST protected by using 5W30 Quaker State Full Synthetic, API SP. And the icing on the cake, is that you can even get great prices on it at Walmart.
5W30 Quaker State Full Synthetic, API SP, is SO GOOD, that it is CLEARLY THE BEST CHOICE for anyone who lives where this oil is available. ANYONE, and I mean ANYONE, who can use 5W30, and has this motor oil available to them, but chooses to use some other oil, has made the WRONG decision.
Since you have to buy motor oil anyway, it is obvious that it makes the most sense to buy the BEST oil while you are at it.
And for the record, I have NO CONNECTION at all to Quaker State. So, what oil anyone chooses to use, does not affect me one way or the other. I am simply sharing the results of my UNBIASED, and 100% HONEST, Engineering Test Data.
So I went and bought a bunch of the Valvoline 75w90 synthetic gear oil.
Going to be honest I’m a little on the fence, granted It’s cold out right now here in North Texas, in the 40s but compared to the motul and the amsoil this Valvoline and my clutch type LSDs don’t like each other.
If I have to put a friction modifier in I suppose I could do that. But I’m trying to stay away from having to buy all these multiple things and creating a witch’s brew. I don’t know. I might look into the amsoil of 75w110.
Either way, thought I’d share. See if you had any opinion. As always, thanks for reading and appreciate your tutelage.
Thanks and talk soon
Paul~
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Hi again Paul,
Valvoline 75W90 Full Synthetic Gear Oil is “FORMULATED FOR and RECOMMENDED FOR” Limited Slip Differentials (LSD). That’s why I recommended it. Do NOT add anything to it.
40+*F weather is not that extreme. That gear oil has been used in countless Limited Slip Differentials. And I have NEVER heard of any complaints before. So, it is odd that you would have an issue.
Saying “they don’t like each other” is not exactly a technical description. Could you be more technically specific about exactly what you are experiencing, and under what conditions, that you did not experience with Motul or Amsoil?
The LSD’s in the front and rear now clatter / chatter pretty strong during slow turning with the Valvoline 75w-40 Synthetic Gear Oil. When before they did not, while using Motul Competition and the Amsoil Gear oils. The LSDs would tighten up during turning and you would here the inner tires (of the turn) skip on the pavement but would not chatter or clatter. If that makes sense?
…Sorry amendment , “…..skip on the pavement but the LSDs* would not chatter or clatter. If that makes sense?”
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It sounds like your particular clutch packs with their particular friction material, are exactly at the grip/slip transition point, to allow turning without tires skidding/wearing on the pavement (which is the whole point of having a clutch pack vs a locked differential) with that Valvoline Gear Oil, at the temperatures they are seeing now.
Does that noise problem go away once the differentials and gear oil are fully warmed-up? If it does, then I would keep the Superior Valvoline Gear oil.
But, if the noise does not go away after being fully warmed-up, then you should not have to live with that noise.
If that is the case, then unfortunately, you will have to give up the Superior Wear Protection Capability and reduced tire wear with that Valvoline Gear Oil. And then you’ll have to go back to one of the other gear oils that will provide less differential wear protection, and cause tire skidding/wear in turns.
As always thanks for your advice and help, means a lot!
You would advise against or condone adding a friction modifier? I’m not opposed to that to try and keep the better protection. Based on your previous comment it seems you warrant against. Curious if it degrades? Ultimately I’m down $200 almost on gear changes so far and would like to use this oil for a bit if I can add a less expensive additive. 😐🤪
If not I’m good to go. 😎
Thanks much and talk soon.
~Paul
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Hi,
Our messages were tripping over each other again. So, go back an reread my response just before this one.
Valvoline says NOT to add anything to this Gear Oil.
To answer you question about the noise and temp. I noticed it intensifies when warmer.
~Paul
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OK, a few last questions.
1. Do you hear the noise during very slow turning such as when maneuvering in a parking lot?
2. Or do you hear the noise in faster turns such as when turning a street/road corner when you did not stop first, in other words, turning a corner while still rolling at a decent mph?
If you are not sure, go test both types of turning with your window open.
3. Are your differential clutch packs stock, or have the clutch friction plates been replaced with “aftermarket” friction plates?
3. No; They are Cusco Type RS LSDs. Which I have arranged the plates to provide 70% Lock, not a full 100% ( which has been working great on the street and track for years now )
(Time to make coffee (5:21am here 😉 ) I assume your blog time is not set?)
Thanks for your help on this!
~Paul
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Hi again Paul,
My Blog is of course on the Internet, so it is available 24/7/365. I don’t have to be here, except to respond to Q&A Messages, or to make updates to the body of the Blog.
OK, we have finally gotten to the “cause” of your issue – which is your AFTERMARKET differentials. That explains why I have never heard of an issue with this Valvoline Gear Oil before. Most other diffs don’t have an issue with it.
We could have saved several back and forth messages if you had mentioned the aftermarket diffs in your first message about this issue – always look at what has been changed from original, first.
That is the kind of thing you can run into with Street/Strip vehicles. They are not quite dedicated Race vehicles, and they are not normal Street vehicles either.
So, you are now between a rock and a hard place. You now have a hard decision to make. Here are your choices:
1. Leave everything “as is” to have the diffs the way you want them, AND to have excellent diff wear protection. You could throttle it up, ignore the noise, or simply turn the radio up. 😊
2. Add some limited slip diff fluid even though Valvoline says it is not needed. And see how it goes.
3. Revise your clutch pack set-up to more or less lock as desired to eliminate the issue. And keep the excellent diff wear protection.
4. Go back to stock diffs, and keep the excellent diff wear protection.
5. Change the gear oil back to what you had before, and accept LESS diff wear protection.
Your call…Let me know what you end up doing, that you are satisfied with.
LOL. No I was referring to the time stamps on comments. e.g. 11:04pm when I posted around 5pm cst. 🙂
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We are tripping over each other’s messages again. Be sure to go back and read my now completed message before this one.
Yeah, my Blog’s time is a default setting that doesn’t mean anything. Texas is 2 hours ahead of me.
Heheh, I was eavesdropping while you where compiling your response and noticed the part about the blog time. 🙂
I notice those things since I’ve ben designing and making sites for the past 18 years.
So I’m going to try #2 and see how it reacts. If it doesn’t improve i’ll switch to Amsoil 75w-110 mainly because when I had the Amsoil 75w-90 my drive train quieted up and smoothed out, noticeably. But hopefully with the 75w-110 I’ll get that same “smoothness” but better wear protection than the 75w-90.
(A Little history) I had been running Motul Competition Gear Oil 75w-140 for years and the times I’ve changed it the magnets on the tranny and rear diff only had SMALL amounts of VERY fine metal deposit [ Like powder ] (I assume LSD clutch plate material). Never any chunks or large build up. Yet I have noticed that with that gear oil the drive train always seemed to be more “vocal” then necessary. Hence going down this path of finding new oils for the ‘ol girl.
So far the Amsoil selection and experience has been great. Just need to find the best balance. (motor oil selection is locked in! 🙂
All I can say so far is I’m grateful for your time all around and many thanks!!!
I’ll keep you posted on my findings with the additive or if I switch.
Thanks as always and lurk mode activated.
~Paul
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😊
Hello Mr. Rat,
I bought some Valvoline synthetic 75w140 gear oil and the LSD friction modifier additive from Ford. The Valvoline description says its recommended for limited slip differentials. I was wondering if that means it can be used as is or if I still need to add LSD friction modifier additive.
Dean
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Hi Dean,
When Gear Oil says it is formulated for Limited Slip differentials, that means it ALREADY HAS the required additives for Limited Slip diffs. So, you use it “as is”. You do NOT have to add anything more to it.
Just leave Ford’s additive on the shelf unopened in case you might need it in the future.
Wonder how much the “wear protection” is effected?
Anyways, thanks again
~Paul
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Hi again Paul,
Awesome! I’m glad to see that took care of your issue.
Hard to say what that does to the wear protection capability of the Valvoline 75W90 Full Synthetic Gear Oil.
All I can say is that I have plenty of data showing that aftermarket motor oil additives, make the motor oil “worse overall” than it was to begin with. But, that may or may not be the same situation here with your gear oil.
And I wonder just how much the differential clutch packs are slipping now, when you don’t want them to. Hopefully, you only added a little Slip Lock to try it out. You can always add more. But, a little at a time allows you to sneak up on it and only use what you need.
Take note of what your inside tires do now in a corner. And see if they still skid the tires on the pavement like previous gear oils did. The tires are not supposed to skid. But, that would be a point of comparison.
In general, just evaluate the performance overall of the diffs and see what you think.
One question for you. How do you get Amsoil products so fast, when virtually no brick and mortar stores carry their products? So, you typically can’t just walk in and buy something.
I always have to order their products, which then typically takes a day or two for an order to arrive. But, you seem to get their products the same day. What’s your secret?
I just seem to luck out. The Amsoil was 2 day delivery time since there is a Amsoil hub near me in the DFW area. The Valvoline happened to be on hand at a local NAPA store and the Slip Lock was on Amazon and showed up next day. (I had ordered it the other day as back up.) 🙂
I saw the discussion here about the 15W50 Mobil 1 a few days ago. Here is my 2 cents on all that.
It seems that many people on car forums consider Mobil 1 to be one of the top oil brands. They just think anything they sell will be top notch.
They have no proof of anything. They just think that Mobil 1 is good based on feelings and not much more. They are swayed by Mobil 1 advertising and by the bottles looking kind of cool. They have no data other than when they have used it, their engines did not blow up.
I’ve used most major oil brands at different times over the years. And I could never really tell any difference. None of my engines ever blew up. As near as I could tell, they all seemed about the same. I could not tell one from the other if I had been put in a blind test of some sort.
Then I found your Blog. With your Engineering Test Data, now we can see exactly how all these oils are different. Thank you for all your efforts. Now we can easily buy the best oil with confidence.
Just for fun, I checked a few auto parts stores in my area. Surprisingly I did find Mobil 1 15W50. They were all the older API SN version. I never did find any with the supposed latest API SP label.
I don’t understand why people want you to test that oil in a newer version. We have all learned from you that low cold viscosity ratings are important during startup and warmup. 0W and 5W oils are desirable. And higher cold viscosity ratings are not desirable. That means 15W50 is not a good choice.
You already have a Mobil 1, 5W50 oil in your air cooled engine article which did very well. That should be good enough for those who just have to have a Mobil 1 oil. Asking for data on 15W50 that is an undesirable viscosity makes no sense to me.
Thanks for everything you do.
Zenyatta
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Hi there,
You are 100% correct on all the points you made. You have been a good student of my Blog, and you have learned well.
Yes, in my Tech Article #69 on air-cooled engine oil, 5W50 Mobil 1, FSX2 did very well. It is ranked 6th out of 15 oils tested there. And with its excellent 5W50 viscosity rating, it is an excellent choice for any air-cooled engine. So, Mobil 1 lovers should be perfectly happy with this oil for air-cooled engines.
Even “IF” a newer version of the regular Mobil 1, 15W50 produced the same psi value as the 5W50 Mobil 1, FSX2, the 15W50 would be a poor choice because of its undesirable 15W cold viscosity rating.
Since that 15W50 Mobil 1 discussion here a few days ago, I went to Walmart and to O’Reilly’s Auto Parts Store, looking for the supposed new API SP version of it. I found regular 15W50 Mobil 1 at both places. But, they both only had the older/current API SN version. So far as I can tell in-person, an API SP version of that oil simply does not exist. At least not in my area.
Since its 15W50 viscosity is undesirable anyway, even if a newer version does eventually show up, it is not worth my time, effort, or money to test it.
It’s the 2022 WRX guy again. As I stated last time my first oil change in the WRX I used Quaker State Full Synthetic with a Wix oil filter.
The factory oil I assume was Subaru 0W-20 (made by Idemitsu)
After the oil change I noticed my oil temperature ran a few degrees cooler. QSFS 5w-30 being thicker should theoretically run slightly warmer?
The outside temperature was the same and even warmer and the QSFS oil just seemed to run cooler in that engine. Oh, the WRX does have a digital oil temperature gauge.
Is it possible that the QSFS reduced friction causes cooler temps?
Again, thanks for all the work you have done. Thought you would be interested in my oil temp observation.
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Hi again,
Yes, I am interested to read about your oil temperature observation. Thanks for sharing.
And yes, traditionally, oil temperatures have typically increased as oil viscosity increases. Because thicker oil flows slower through the engine, and does not cool as well.
0W16, 0W20 and 5W20 are thinner than ideal. And are only intended to possibly, ever so slightly improve gas mileage. Though Owners can never measure any advantage compared to 0W30 or 5W30.
0W30 and 5W30 are “THE IDEAL” viscosity OVERALL for flow, lubrication, cooling, minimizing mechanical engine noise, and for engine wear protection, especially when run aggressively.
In addition to that, the fairly recent API SP revision, especially in the case of 5W30 Quaker State Full Synthetic, API SP, has approached being a Revolutionary change, rather than merely an Evolutionary change.
And yes, its friction reduction formulation reduces heat. Because friction means heat. So, less friction equals less heat.
We are fortunate to have the truly impressive 5W30 Quaker State Full Synthetic, API SP, readily available to us. And we can even get good prices on it at Walmart.
Seeing as how no oil manufacturer is to be trusted in relaying to the public any formulation changes to their oils, do you think it would be prudent to retest the top tier oil/oils in your list every two years or so? I know I would be willing to chip in for the costs and I bet more of your followers would feel the same just for the peace of mind.
Thanks for all you do!
Rich
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Hi Rich,
In a perfect world, that might be something to consider. But, performing my Engineering Torture Test on motor oil, is a huge effort, and takes a lot of time, money aside. So, it simply is not feasible to endlessly test oils.
My Engineering Tests have clearly shown, essentially the only motor oils today that are truly “Top Tier” performing oils, are some of the better, latest API SP oils.
None of the other motor oils even matter. Because the poor performing API SP and non-API motor oils should not be used, if people care about their engines.
We know when API motor oils are reformulated by changes in API certification, such as when they made the significant change from API SN Plus, to API SP.
If they were to change their oils for the worse, they would no longer meet their standing API certification, and could no longer legally be sold showing that standing certification.
With API certified oils in the past, it has been clear that a change was made, be it an API revision, or product name change. That was the case when Castrol ruined their oils. They had name changes and/or API revisions, which is what prompted me to retest them. That’s when I caught them in the act of ruining their oils.
The extremely poor performance of non-API oils such as High Zinc Racing Oils, etc, are really irrelevant, and are not worth retesting. So, we don’t care if they secretly change their formulations.
In the real world, I now typically retest the better performing oils only at API changes, which are significant. That is enough to ensure that we are getting what we need/want.
(First, I want to ask, do you default see my previous posts on your monitor, or do you have to scroll back, manually?)
So far, I’ve figured out to receive a big box of super fine Amsoil 10W50 DirtBike oil (for a acceptable price), and replaced the timing chain.
But, the Quaker State QSFS for my cars….. No official EU-import company is found, yet. QuakerState.com don’t reply.. I only got in contact with some “local” US sparepart importers, which calculated prices between $49-58 pr. Quart! (NOT a typo) So I’m still searching 😉
During (previously) investigation, I discovered this engine oil tests, in EU:
1.a. Engine oil shear test.
XXX…
1.b. Results of shear tests.
XXX…
I’m all sure, you have some comments to this test…..
And NOT to forget, I’m still both very interested & impressed regarding this fabulous oil blog, THANK YOU!
Take care Sir!
KR.
Carsten.
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Hi again Carsten,
I have to scroll back manually to see your previous posts.
I do not allow links in my Blog. But, I did view both links you sent me, then I deleted them.
I do have a comment about that oil test. A lot of time and effort was obviously spent on that test. And he wants to charge people money to see more of it.
However, it clearly did NOT involve qualified, Degreed Mechanical Engineers. So unfortunately, it is crudely designed and poorly executed, making it just worthless garbage.
If you want to see Accurate and Reliable Engineering Test Data, that has been “PROVEN” TO EXACTLY MATCH real world experience, you still need to come to my Blog. Then look at my “Wear Protection Ranking List”, that you can easily make use of the next time you buy motor oil.
Thank you so much Rat!
Surely, I (only) use your results, regarding oil for my water- and aircooled engines, gearbox and differentials.
If I cannot get the QSFS 5W30, chances for the Amsoil Signatures Series are better, but, so far, I’ve only got the 10W30 option, and that is to thick for winter use.
I’ll keep you informed what’s going on “over here”… 😉
Keep safe,
Carsten.
540 RAT - Tech Facts, NOT Myths 
Good afternoon, 540 RAT,
On a 2008 Mercedes-Benz E550, the owner’s manual calls for 85W-90 hypoid gear oil to be used in the rear differential on a car. However, there are very few suppliers of 85W-90 hypoid gear oil, one of them LiquiMoly and another one is buying OEM fluids from the dealership.
I don’t want to run LiquiMoly gear oil for reasons that you’ve shared with us. And, it is likely that LiquiMoly supplies Mercedes-Benz with the same gear oil used in OEM packaging (though I haven’t checked).
Do you think it would be okay to use Valvoline 80W-90 High Performance Hypoid gear oil, ranked #5 on your gear oil/transmission oil testing list, inside that rear differential?
Thank you for your help in advance,
Sam
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Hi Sam,
Valvoline 80W-90 High Performance, “conventional” GL-5 hypoid extreme pressure gear oil would be a good choice for conventional differentials. But, it is “NOT” for limited slip differentials.
Valvoline 75W-90 Full “Synthetic”, GL-5 hypoid extreme pressure gear oil is a good choice for conventional “OR” limited slip differentials.
So, choose between either one of these as needed for your vehicle, and you will good to go.
Take care,
540 RAT
Hello Mr. Rat,
Public service announcement with regards to hybrid and plug in hybrid. The extra money you pay up front may be offset by gas savings ( only if the majority of driving is “city” ) but then all those break even savings are lost when you have to fix/replace the battery and other associated repairs due to its complexity.
Dean
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Hi Dean,
Yes, you are correct.
Take care,
540 RAT
Morning 540 Rat-
Subaru “Hybrid” motor guy again. 8)
Was wondering (after f3’ing my brains out) if you have plans to ever test Amsoil Signature Series 0W-40 Synthetic Motor Oil?
Thanks for reading and have a good day
~Paul
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Hi again Paul,
No, because a multi-viscosity 40wt motor oil is THICKER than ideal for most water-cooled, gasoline engine applications.
And a multi-viscosity 20wt motor oil is THINNER than ideal for most most water-cooled, gasoline engine applications.
But, a multi-viscosity 30wt motor oil is THE IDEAL viscosity for most most water-cooled, gasoline engine applications.
Since it is just not possible to test every last motor oil on the market, I focus mostly on multi-viscosity 30wt motor oils, that have the highest value, for the most people.
However, the Amsoil Signature Series line of oil, is very good. So, for your particular application, you could run 0W40 Amsoil Signature Series with no concern at all, even if I have not tested it.
If I owned your particular High Horsepower WRX STi, with its marginal bottom end design, I would use 0W40 Amsoil Signature Series, so that I could sleep better at night.
Your car is an exception where a multi-viscosity 30wt motor oil is NOT the best choice. You will kick yourself if you blow your engine up from running the wrong viscosity motor oil, when you have been made aware of the viscosity that is the BEST choice for you to be running.
People doing the right thing, don’t blow-up their engine. That’s why I recommended you use 0W40 Amsoil Signature Series. Because it is the BEST choice for your particular application, and will provide a higher “Margin of Safety”, as we call it in Engineering.
As I have said before, for most cases, here is how a motor oil should be chosen, in this exact order:
1. Select the correct viscosity.
2. Select a highly ranked, high psi oil from my Wear Protection Ranking List.
However, for any questions about special cases, get in touch with me here.
I make Engineering recommendations based on each specific application I am asked about. But of course, each reader ultimately has to decide for themselves, what they want to do with that recommendation.
Take care,
540 RAT
Hey 540 Rat-
Bad ass!! Love it here. Thanks for the advise. Wish I could buy yah beer (if you drink 🙂 )
Thanks much and talk soon. I’ll be lurking.
~Paul
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Lurkers are always welcome. 😊
540 RAT
Rat-
First off, thanks for this work you’ve committed yourself to for years now. I’ve been following it for about 4 years on and off.
So let me get to it: I own a VW.
The 5w30 QSFS isn’t euro rated for VW. I did find a QSFS 5w40 euro that rates pretty well on your testing but I wanted to ask how important is the Euro tag on the bottle?
Can I run the QSFS 5w30?
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Hi David,
Thanks for being one of my many Blog followers.
If your VW has a Diesel engine, then you should use a “Euro” motor oil.
If your VW has a gasoline engine, then 5W30 QSFS (Quaker State Full Synthetic), API SP, would be the BEST choice.
Take care,
540 RAT
Hey 540Rat-
Subaru “Hybrid” guy, again.
So as cheesy as it might sound and based on what I can hear, see, as well as my butt dyno / ass sensor inputs are telling me, the Amsoil 0W40 signature series seems to be a great match for my build/motor. It actually smoothed out the idle a small amount, enough to notice! Power feels more linear and pushes sooner in the lower RPM range.
I also went and put in Amsoil 75W90 severe gear oil and even that made a difference in the sense that the drive train noise quieted down and smoothed out as well, including a smoother shift through the gears!!
Crazy! Well thought I’d share….back to lurk mode
Thanks for reading.
-Paul
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Hi again Paul,
Hopefully, you will be lurking again soon to read my response here.
Two things, one GOOD, and one BAD:
1. GOOD – I’m glad to see that you are very happy with the 0W40 Amsoil Signature Series oil that I recommended specifically for your build/motor.
2. BAD – You obviously have not read my Tech Article #55 on Gear Oil Tests.
If you had, you would know that 75W90 Amsoil Severe Gear Oil was THE WORST performing gear oil I tested. It is ranked 11th out of the 11 Gear Oils I tested. It is one of Amsoil’s WORST performing products.
My strong recommendation is for this gear oil to NEVER be used. One of my other Blog readers reported that he and his buddies were getting a lot of metal particles on their differential magnetic drain plugs when using this gear oil. When they changed to a better gear oil from my Gear Oil Test, the metal particles disappeared.
NOTE: The HIGHER the psi value, the BETTER the Wear Protection. Here are the comparison numbers:
75W90 Amsoil Severe Gear Oil = ONLY 78,481 psi
75W-90 Valvoline Full Synthetic Gear Oil = 121,502 psi
So as you can see, the 75W-90 Valvoline Full Synthetic Gear Oil provides a WHOPPING 55% MORE WEAR PROTECTION than that pathetic 75W90 Amsoil Severe Gear Oil.
So you should replace that Amsoil gear oil ASAP.
Take care,
540 RAT
Hey 540Rat-
I did see that section, but I had impulse ordered that and was about to return it for the 75W110 version but decided to run this for a short period as like a flush to get the Motul out.
I’ll give the Valvoline a look!
Thanks as always!
~Paul
Hi 540 RAT,
I saw some good News today. Now GM says they are not abandoning their gas V-8 engines after all, to switch to all electric vehicles only. That really surprised me because GM’s CEO has prided herself in being a radical climate fanatic. I guess she finally got a clue that GM would collapse if they only offer electric vehicles. Your thoughts?
Zenyatta
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Hi again,
Yes, I saw that in the News also. And that did come as a total surprise. Because GM’s utterly worthless and completely incompetent CEO Mary Barra, has for a long time been saying “matter of factly” that GM was converting to an All-EV Company by 2030 or 2035, depending on which News article you read. And absolutely no exceptions were ever mentioned.
Now today, she back-pedaled and GM announced that they are NOT going to abandon their gas engines. They said they will still offer gas V-8’s in their full-size pick-ups, SUV’s, and larger trucks. And they said they are investing nearly a $billion dollars in 4 new factories to produce those engines.
Making such an abrupt reversal in their future plans, would make you think that much smarter people than her at GM, could see they were heading toward the cliff of extinction, perhaps from Market Research.
Because it is quite clear that Americans simply do NOT want EV’s which are THE WORST vehicles ever created. They are miserable to live with, and many EV buyers are suffering massive buyer’s remorse.
Especially as more and more buyers discover that in freezing weather, EV’s are simply unworkable because of 50% reductions in driving range and EXTREME DIFFICULTIES in recharging. One owner of a new very expensive Hummer EV, found out that the largest home charger you can buy, took 5 DAYS, yes 5 DAYS to fully recharge his Hummer. He had major buyer’s remorse.
So, you have to wonder if GM’s Board of Directors told CEO Mary Barra to make some serious changes if she wanted to keep her job.
Whatever the case, that is a major move in the right direction for GM. And with Ford already planning separate Gas and Electric Divisions, now it will be interesting to see if Chrysler revises their All-Electric plans, now that they are the only major American Automaker claiming to be switching to all EV’s. TBD…
Take care,
540 RAT
Good Morning.
Very Interesting Blog. I appreciate the view. Interesting on the PSI and not so much on the traditional ZDDP and or truck oil.
I have seen this blog many times. I have read through it.
I have had failures in the past, and I have had good results. I dont want to name oils here.
so…to my questions…or I am soliciting a recommendation from you…
I am running a 427 cubic inch Ford windsor engine(stroked 351) with a dart block and eagle steel crank-rods. I run a solid roller cam with pressure fed solid roller lifters. Makes an Honest 680hp on the dyno. 12 to 1 compression. I run high octane gas–110
To date, I have run rotella 15/40w dino and mobil 1 15/50 synthetic. No reliability issues to date, low use, under 20 hrs. Maybe 10-20 runs at the drag strip. To date, the rotella was faster than the mobil 1 15/50….
I want a lighter oil. I want a reliable oil. I see your list.
I have been told the Mobil1 0w40 is a good hearty oil..its a Heavy 30wt not really a full 40wt), I see it on your list. I also see the mobil 1 racing 5w30 on your list…(shocked at your rating -psi).
Would you care to recommend an oil?
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Hi Harry,
As you are probably aware, roller motors are not finicky about what oil they use, like flat tappet motors are. So, roller motors can use many different oils without any major issue.
But, the fact that you are here asking for a recommendation, indicates you would like to run an excellent motor oil that will provide the best wear protection for your engine.
You came to the right place for CORRECT/FACTUAL Engineering information that is backed-up by hard Engineering Test Data. I am the ONLY one anywhere, who backs-up everything I post with hard data, proving everything I say.
You will only find reliable and accurate information right here in my Engineering Blog. I started my Blog 10 years ago so that Car Guys would FINALLY have some place to go for TRUE information.
And I have numerous Blog reader testimonials in the body of my Blog, PROVING that my Engineering Test Data EXACTLY MATCHES real world experience.
The notions that High Performance engines need High ZDDP and/or Heavy Duty Diesel oils, are pure nonsense. They are only MYTHS that were just “made-up” by unqualified and incompetent people. And now they are perpetuated on Automotive Forums and elsewhere, by people who have no idea what they are talking about. But of course, repeating BAD/WRONG information a million times, does NOT make it magically become true.
Anything you read or are told about motor oil that is not backed-up by hard Engineering Test Data, is only opinion, theory, speculation, or guessing.
The fact is, Engineering Test Data has PROVEN over and over again, that Heavy Duty Diesel oils produce low psi numbers, and they reach the onset of thermal breakdown sooner than the better, far superior gas engine oils.
Also, experience and Engineering Test Data, have shown time and time again, that High ZDDP motor oils, including Break-In oils, typically produce very low psi numbers, and actually are very likely to CAUSE wear, damage and failure. That’s why flat tappet engines keep wiping lobes when they use High ZDDP oils.
ZDDP is just an old, outdated, obsolete anti-wear component from the last century. It has been FAR SURPASSED by modern, proprietary, 21st century anti-wear formulations. That’s why many new API SP motor oils are SO MUCH BETTER than old style high ZDDP oils. Hotrodders and Racers need to get with the program and switch to the newer oils, if they want the best protection for their engines.
When it comes to the TRUTH about motor oil wear protection capability, the ONLY thing that matters, is the psi value an oil can produce in my Engineering Torture Test on motor oil. The HIGHER the psi value, the BETTER the wear protection capability.
*****
You did not say what sort of engine clearances you are running, nor if you are running a standard volume oil pump, or a high volume oil pump. Both of those have a great impact on the “HOT” oil pressure your engine is capable of generating.
The old rule of thumb for High Performance and Racing engines, is that they should produce “at least” 10 psi of “HOT” oil pressure at normal operating temperature, for every 1,000 rpm. For example, you want to see “at least” 40 psi of “HOT” oil pressure at 4,000 rpm, etc, etc.
My number 1, All-Time BEST, Record Setting psi motor oil, which produces THE BEST Wear Protection Capability ever recorded, is modern 5W30 Quaker State Full Synthetic (QSFS), API SP. And you can even get great prices on it at Walmart.
I use 5W30 QSFS in ALL of my own engines, including old school flat tappet, modern stock and High Performance, big cubic inch, and Supercharged.
I have numerous Drag Racer readers who use that 5W30 QSFS oil in their old school flat tappet race engines, with GREAT success.
So, “IF” your engine can generate acceptable “HOT” oil pressure with a 5W30 motor oil, that oil is your answer for a lighter, reliable oil.
With all other things being equal, the thinner/lighter the motor oil, the quicker your car will be at the Drag Strip, because of less viscous drag, which frees more HP to move the car.
However, if your engine requires a thicker oil to maintain acceptable “ HOT” oil pressure, then I recommend using 0W40 Amsoil Signature Series motor oil.
Take care,
540 RAT
Morning 540Rat-
Just to clarify, I found 2 types of packaging for the Valvoline gear oil. So wanted to ask which is the one you tested? Please and thanks.
1. Valvoline FlexFill Full Synthetic 75W-90
2. Valvoline SynPower 75W-90
Thanks much and talk soon
~Paul
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Hi again Paul,
I tested Valvoline FlexFill Full Synthetic 75W-90. That is the one you want. Just so you know, “FlexFill” is only a reference to the container the gear oil comes in, which often makes it more convenient to put in the vehicle. But, the gear oil itself is called “Valvoline Full Synthetic 75W-90”.
Valvoline SynPower 75W-90 is an older gear oil Valvoline no longer produces, and is no longer shown on their website. Though there is likely a lot of it still in warehouses.
And they have dropped the “SynPower” name, which is no longer on their current products.
Take care,
540 RAT
540Rat-
Roger that!!!
Thanks as always
~Paul
Hello 540Rat.
I looked at Mobil 1’s website and at their product data sheet and saw that their 15w50 is now API SP rated as well the FS 0w40and FS 5w40 . I talked to a rep at Mobil 1 to confirm and he said “this is correct.” I was wondering if you would be testing any of those for air-cooled equipment? Thanks again! – Joe
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Hi Joe,
Here we go again. That Mobil 1, 15W50 was the source of some uncomfortable discussions here a few months ago, regarding whether or not it was really API SP.
At that time, I could not find anywhere on their website showing that it was really API SP. And I could not find an API SP version in person either.
But, one of my readers insisted it was API SP. He even sent a picture of it showing API SP. So, the whole thing was a total mess. And I said I would not touch that Frankenstein oil with a 10 foot pole.
Now, I just looked at TWO different Mobil 1 links, and AGAIN, including their product data sheet, neither one showed it as API SP. Apparently Mobil 1 is incompetent. They can’t even get their website right.
I don’t know what you are looking at on-line that shows it as API SP. But, if it is that hard to find, I would not trust it.
If I ever come across Mobil 1, 15W50 in person that has API SP on the bottle, I “might” get one to test.
But, I’m not as much of a fan of Mobil 1 oils, as some of my readers are. Because their performance is very inconsistent on psi value, and their performance at higher temperatures can be rather poor as well.
I never use Mobil 1 oils myself, and I never recommend their oils either. So, I would have to decide if testing a newer version of their 15W50 is worth my time, effort, and money.
Plus, I lost all respect for the Mobil 1 Brand when they came out with their extremely poor performing 5W30 Annual Protection oil, which is ranked a pathetic 178th out of 286 motor oils tested so far. That oil is a TOTAL scam from a dishonest Company, that is only intended to separate gullible people from their money.
And their prior/current Mobil 1, 15W50 is horrible, with a value of only 70,235 psi, which ranks it a miserable 237th out of 286 oils tested so far. So, I wouldn’t hold my breath for a newer version to be WAY better.
There are plenty of other oils, and some are quite good, to choose from in my Tech Article on Air-Cooled Engine Oils. So, no one “needs” another Mobil 1 oil.
XW40 oils are NOT thick enough to be acceptable choices for air-cooled engines.
Only XW50 and XW60 oils are truly suitable for air-cooled engines.
You can NEVER trust anything a Company Rep ever says. They are every bit as bad as a Used Car Salesmen.
Take care,
540 RAT
Hello Mr. Rat,
I was Canadian Tire today looking for deals on oil and the only one on sale was the Mobil 1 annual protection. I initially thought it should be at least as good as their other stuff because its Mobil synthetic – and then the rational part of my brain kicked in and said don’t buy it unless I see some psi numbers! Glad I happened upon this QandA.
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Hi Dean,
The is “no guarantee” that a Mobil 1 Synthetic motor oil will automatically be a good oil. There are a good number of Mobil 1 Synthetic motor oils that are poor performers that are not worth using.
For some reason, people tend to think all Mobil 1 oils are great. But, that is simply NOT true. All anyone has to do is read through my whole Wear Protection Ranking List.
Then they can see for themselves, that some Mobil 1 oils perform well, and some Mobil 1 oils perform poorly. But, you cannot know which is which until you look through my Ranking List.
Mobil 1 Annual Protection was “On Sale” for one reason. It is because that overly expensive, poor performing oil, was discontinued after one year because of poor sales.
So now, places that have it in stock, are still trying to dump their old stock of it by putting it “On Sale” just to get rid of it.
You did the right thing by avoiding it. Because it is not worth using even if it was free. A massive 177 other motor oils on my Ranking List perform BETTER than that oil.
Take care,
540 RAT
Hello again 540Rat,
Motul 75w90 is out of stock just about everywhere. Those that do have it in stock want ridiculous $$$ per quart.
Is there an alternative gear oil you would recommend since the Motul is unobtanium?
Thanks again for all your hard work!
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Hi again,
I’m not sure why you would think that Motul Gear Oil is “The Gear Oil” to use. Because there is “nothing” special about Motul. It is NOT the Best performing Brand. Motul is just another “ordinary” Brand.
But, I suspect Automotive Forum people say Motul is the greatest Brand out there. However, Automotive Forums only throw out Bad/Wrong information. Because the unqualified people there have no idea what they are talking about. Automotive Forums are THE WORST places to ever go for information.
I started my Engineering Blog 10 years ago, so that Car Guys would FINALLY have a place to go for the “Truth”.
Not only do I have an alternative to Motul Gear Oil for you, I have a “Significantly Superior” Gear Oil for you.
In my Engineering Torture Test on Lubricating Oils, these two Gear Oils produced:
Motul 75W90 Gear 300 Fluid = 103,868 psi
Valvoline 75W-90 Full Synthetic Gear Oil = 121,502 psi, which provides 17% BETTER WEAR PROTECTION than the Motul 75W90.
NOTE: The HIGHER the psi value, the BETTER the Wear Protection Capability.
So, if you use Valvoline 75W-90 Full Synthetic Gear Oil, you will be MUCH BETTER OFF, than if you used the Motul you originally had in mind.
Take care,
540 RAT
Hey Rat,
Thought you’d be interested in my oil report on the Coyote with the first fill of QSFS 5w30 – by comparison, *significantly* less iron and less overall other wear metals than the previous test which ran Pennzoil Platinum 5w30. That was also during harder working conditions for the engine (cold, short runs etc.)
Once again, the regional(?) Costco Kirkland Signature 5w30 oil is on sale (among their other offerings, including a diesel oil) and i was reminded that other, lesser testing than you perform, showed it to be a pretty reasonable oil, especially for the price, then remembered you didn’t have a test of it 😀
The recent gear oil discussions reminded me that i needed to order some more Valvoline 75w90 for the front diff as it’s due a change, i do like the Flexfill containers, they were really convenient on the Amsoil 75w140.
Take care
Maxx,
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Hi again Maxx,
No, I have not tested Costco/Kirkland labeled 5W30 motor oil because their Management refused to sell me single quart to test. And I was not about to buy a case of low priced, low quality motor oil, just to test one quart, then dump the whole rest of the case. So, I will never test that oil.
Do NOT be gullible enough to believe that any “lesser” testing on motor oil has any value at all.
I spent a LOT of time, a LOT of effort, and a LOT of money, drawing from my years as a Professional Mechanical Engineer and Car Guy, to develop my proprietary Engineering Test Protocol on motor oil, that EXACTLY matches real world experience.
NO ONE ELSE ANYWHERE, has access to my Engineering Test Protocol. Because it is my own Intellectual Property that will never be shared. So, my Engineering Test Data is the ONLY Test Data that is accurate and reliable.
Thanks for sharing the info on your 5W30 QSFS (Quaker State Full Synthetic, for those not familiar with the abbreviation) used oil Lab Test report.
That is yet another validation of the accuracy of my Engineering Torture Test on motor oil, which shows 5W30 QSFS to provide THE BEST wear protection on the market today.
It is ranked “NUMBER 1”, producing an amazing 152,674 psi, which is the HIGHEST/BEST value ever recorded for wear protection capability, out of a whopping 286 motor oils tested so far.
EVERY Race, traditional flat tappet, Supercharged, Turbocharged, European, and Motorcycle, water-cooled, gas engine that can use 5W30, is BEST served and BEST protected by using 5W30 Quaker State Full Synthetic, API SP. And the icing on the cake, is that you can even get great prices on it at Walmart.
5W30 Quaker State Full Synthetic, API SP, is SO GOOD, that it is CLEARLY THE BEST CHOICE for anyone who lives where this oil is available. ANYONE, and I mean ANYONE, who can use 5W30, and has this motor oil available to them, but chooses to use some other oil, has made the WRONG decision.
Since you have to buy motor oil anyway, it is obvious that it makes the most sense to buy the BEST oil while you are at it.
And for the record, I have NO CONNECTION at all to Quaker State. So, what oil anyone chooses to use, does not affect me one way or the other. I am simply sharing the results of my UNBIASED, and 100% HONEST, Engineering Test Data.
Take care,
540 RAT
Hey 540 Rat-
Paul, the Subaru “hybrid” guy again.
So I went and bought a bunch of the Valvoline 75w90 synthetic gear oil.
Going to be honest I’m a little on the fence, granted It’s cold out right now here in North Texas, in the 40s but compared to the motul and the amsoil this Valvoline and my clutch type LSDs don’t like each other.
If I have to put a friction modifier in I suppose I could do that. But I’m trying to stay away from having to buy all these multiple things and creating a witch’s brew. I don’t know. I might look into the amsoil of 75w110.
Either way, thought I’d share. See if you had any opinion. As always, thanks for reading and appreciate your tutelage.
Thanks and talk soon
Paul~
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Hi again Paul,
Valvoline 75W90 Full Synthetic Gear Oil is “FORMULATED FOR and RECOMMENDED FOR” Limited Slip Differentials (LSD). That’s why I recommended it. Do NOT add anything to it.
40+*F weather is not that extreme. That gear oil has been used in countless Limited Slip Differentials. And I have NEVER heard of any complaints before. So, it is odd that you would have an issue.
Saying “they don’t like each other” is not exactly a technical description. Could you be more technically specific about exactly what you are experiencing, and under what conditions, that you did not experience with Motul or Amsoil?
Your concern isn’t just a “feeling” is it?
Take care
540 RAT
Hey 540 Rat-
Sorry about that.
The LSD’s in the front and rear now clatter / chatter pretty strong during slow turning with the Valvoline 75w-40 Synthetic Gear Oil. When before they did not, while using Motul Competition and the Amsoil Gear oils. The LSDs would tighten up during turning and you would here the inner tires (of the turn) skip on the pavement but would not chatter or clatter. If that makes sense?
Thank
~Paul
…Sorry amendment , “…..skip on the pavement but the LSDs* would not chatter or clatter. If that makes sense?”
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It sounds like your particular clutch packs with their particular friction material, are exactly at the grip/slip transition point, to allow turning without tires skidding/wearing on the pavement (which is the whole point of having a clutch pack vs a locked differential) with that Valvoline Gear Oil, at the temperatures they are seeing now.
Does that noise problem go away once the differentials and gear oil are fully warmed-up? If it does, then I would keep the Superior Valvoline Gear oil.
But, if the noise does not go away after being fully warmed-up, then you should not have to live with that noise.
If that is the case, then unfortunately, you will have to give up the Superior Wear Protection Capability and reduced tire wear with that Valvoline Gear Oil. And then you’ll have to go back to one of the other gear oils that will provide less differential wear protection, and cause tire skidding/wear in turns.
Take care,
540 RAT
Hey 540 Rat-
As always thanks for your advice and help, means a lot!
You would advise against or condone adding a friction modifier? I’m not opposed to that to try and keep the better protection. Based on your previous comment it seems you warrant against. Curious if it degrades? Ultimately I’m down $200 almost on gear changes so far and would like to use this oil for a bit if I can add a less expensive additive. 😐🤪
If not I’m good to go. 😎
Thanks much and talk soon.
~Paul
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Hi,
Our messages were tripping over each other again. So, go back an reread my response just before this one.
Valvoline says NOT to add anything to this Gear Oil.
540 RAT
To answer you question about the noise and temp. I noticed it intensifies when warmer.
~Paul
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OK, a few last questions.
1. Do you hear the noise during very slow turning such as when maneuvering in a parking lot?
2. Or do you hear the noise in faster turns such as when turning a street/road corner when you did not stop first, in other words, turning a corner while still rolling at a decent mph?
If you are not sure, go test both types of turning with your window open.
3. Are your differential clutch packs stock, or have the clutch friction plates been replaced with “aftermarket” friction plates?
Take care,
540 RAT
Morning 540 Rat-
Answers:
1. Yes.
2. Yes; If I throttle up it lessens.
3. No; They are Cusco Type RS LSDs. Which I have arranged the plates to provide 70% Lock, not a full 100% ( which has been working great on the street and track for years now )
(Time to make coffee (5:21am here 😉 ) I assume your blog time is not set?)
Thanks for your help on this!
~Paul
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Hi again Paul,
My Blog is of course on the Internet, so it is available 24/7/365. I don’t have to be here, except to respond to Q&A Messages, or to make updates to the body of the Blog.
OK, we have finally gotten to the “cause” of your issue – which is your AFTERMARKET differentials. That explains why I have never heard of an issue with this Valvoline Gear Oil before. Most other diffs don’t have an issue with it.
We could have saved several back and forth messages if you had mentioned the aftermarket diffs in your first message about this issue – always look at what has been changed from original, first.
That is the kind of thing you can run into with Street/Strip vehicles. They are not quite dedicated Race vehicles, and they are not normal Street vehicles either.
So, you are now between a rock and a hard place. You now have a hard decision to make. Here are your choices:
1. Leave everything “as is” to have the diffs the way you want them, AND to have excellent diff wear protection. You could throttle it up, ignore the noise, or simply turn the radio up. 😊
2. Add some limited slip diff fluid even though Valvoline says it is not needed. And see how it goes.
3. Revise your clutch pack set-up to more or less lock as desired to eliminate the issue. And keep the excellent diff wear protection.
4. Go back to stock diffs, and keep the excellent diff wear protection.
5. Change the gear oil back to what you had before, and accept LESS diff wear protection.
Your call…Let me know what you end up doing, that you are satisfied with.
Ah, the joys of living with Street/Strip cars.
Good Luck,
540 RAT
LOL. No I was referring to the time stamps on comments. e.g. 11:04pm when I posted around 5pm cst. 🙂
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We are tripping over each other’s messages again. Be sure to go back and read my now completed message before this one.
Yeah, my Blog’s time is a default setting that doesn’t mean anything. Texas is 2 hours ahead of me.
540 RAT
Hey 540 Rat-
Heheh, I was eavesdropping while you where compiling your response and noticed the part about the blog time. 🙂
I notice those things since I’ve ben designing and making sites for the past 18 years.
So I’m going to try #2 and see how it reacts. If it doesn’t improve i’ll switch to Amsoil 75w-110 mainly because when I had the Amsoil 75w-90 my drive train quieted up and smoothed out, noticeably. But hopefully with the 75w-110 I’ll get that same “smoothness” but better wear protection than the 75w-90.
(A Little history) I had been running Motul Competition Gear Oil 75w-140 for years and the times I’ve changed it the magnets on the tranny and rear diff only had SMALL amounts of VERY fine metal deposit [ Like powder ] (I assume LSD clutch plate material). Never any chunks or large build up. Yet I have noticed that with that gear oil the drive train always seemed to be more “vocal” then necessary. Hence going down this path of finding new oils for the ‘ol girl.
So far the Amsoil selection and experience has been great. Just need to find the best balance. (motor oil selection is locked in! 🙂
All I can say so far is I’m grateful for your time all around and many thanks!!!
I’ll keep you posted on my findings with the additive or if I switch.
Thanks as always and lurk mode activated.
~Paul
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😊
540 RAT
Hello Mr. Rat,
I bought some Valvoline synthetic 75w140 gear oil and the LSD friction modifier additive from Ford. The Valvoline description says its recommended for limited slip differentials. I was wondering if that means it can be used as is or if I still need to add LSD friction modifier additive.
Dean
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Hi Dean,
When Gear Oil says it is formulated for Limited Slip differentials, that means it ALREADY HAS the required additives for Limited Slip diffs. So, you use it “as is”. You do NOT have to add anything more to it.
Just leave Ford’s additive on the shelf unopened in case you might need it in the future.
Take care,
540 RAT
Hi 540 Rat-
Update:
Well went and put in some of this.
Amsoil Slip Lock Differential Additive.
And the clatter / chatter went away. 🙂
Wonder how much the “wear protection” is effected?
Anyways, thanks again
~Paul
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Hi again Paul,
Awesome! I’m glad to see that took care of your issue.
Hard to say what that does to the wear protection capability of the Valvoline 75W90 Full Synthetic Gear Oil.
All I can say is that I have plenty of data showing that aftermarket motor oil additives, make the motor oil “worse overall” than it was to begin with. But, that may or may not be the same situation here with your gear oil.
And I wonder just how much the differential clutch packs are slipping now, when you don’t want them to. Hopefully, you only added a little Slip Lock to try it out. You can always add more. But, a little at a time allows you to sneak up on it and only use what you need.
Take note of what your inside tires do now in a corner. And see if they still skid the tires on the pavement like previous gear oils did. The tires are not supposed to skid. But, that would be a point of comparison.
In general, just evaluate the performance overall of the diffs and see what you think.
One question for you. How do you get Amsoil products so fast, when virtually no brick and mortar stores carry their products? So, you typically can’t just walk in and buy something.
I always have to order their products, which then typically takes a day or two for an order to arrive. But, you seem to get their products the same day. What’s your secret?
Take care,
540 RAT
Hey 540 Rat-
I just seem to luck out. The Amsoil was 2 day delivery time since there is a Amsoil hub near me in the DFW area. The Valvoline happened to be on hand at a local NAPA store and the Slip Lock was on Amazon and showed up next day. (I had ordered it the other day as back up.) 🙂
Have a good night!
~Paul
Hi RAT,
I saw the discussion here about the 15W50 Mobil 1 a few days ago. Here is my 2 cents on all that.
It seems that many people on car forums consider Mobil 1 to be one of the top oil brands. They just think anything they sell will be top notch.
They have no proof of anything. They just think that Mobil 1 is good based on feelings and not much more. They are swayed by Mobil 1 advertising and by the bottles looking kind of cool. They have no data other than when they have used it, their engines did not blow up.
I’ve used most major oil brands at different times over the years. And I could never really tell any difference. None of my engines ever blew up. As near as I could tell, they all seemed about the same. I could not tell one from the other if I had been put in a blind test of some sort.
Then I found your Blog. With your Engineering Test Data, now we can see exactly how all these oils are different. Thank you for all your efforts. Now we can easily buy the best oil with confidence.
Just for fun, I checked a few auto parts stores in my area. Surprisingly I did find Mobil 1 15W50. They were all the older API SN version. I never did find any with the supposed latest API SP label.
I don’t understand why people want you to test that oil in a newer version. We have all learned from you that low cold viscosity ratings are important during startup and warmup. 0W and 5W oils are desirable. And higher cold viscosity ratings are not desirable. That means 15W50 is not a good choice.
You already have a Mobil 1, 5W50 oil in your air cooled engine article which did very well. That should be good enough for those who just have to have a Mobil 1 oil. Asking for data on 15W50 that is an undesirable viscosity makes no sense to me.
Thanks for everything you do.
Zenyatta
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Hi there,
You are 100% correct on all the points you made. You have been a good student of my Blog, and you have learned well.
Yes, in my Tech Article #69 on air-cooled engine oil, 5W50 Mobil 1, FSX2 did very well. It is ranked 6th out of 15 oils tested there. And with its excellent 5W50 viscosity rating, it is an excellent choice for any air-cooled engine. So, Mobil 1 lovers should be perfectly happy with this oil for air-cooled engines.
Even “IF” a newer version of the regular Mobil 1, 15W50 produced the same psi value as the 5W50 Mobil 1, FSX2, the 15W50 would be a poor choice because of its undesirable 15W cold viscosity rating.
Since that 15W50 Mobil 1 discussion here a few days ago, I went to Walmart and to O’Reilly’s Auto Parts Store, looking for the supposed new API SP version of it. I found regular 15W50 Mobil 1 at both places. But, they both only had the older/current API SN version. So far as I can tell in-person, an API SP version of that oil simply does not exist. At least not in my area.
Since its 15W50 viscosity is undesirable anyway, even if a newer version does eventually show up, it is not worth my time, effort, or money to test it.
Thanks for your 2 cents worth,
540 RAT
Howdy 540 Rat,
It’s the 2022 WRX guy again. As I stated last time my first oil change in the WRX I used Quaker State Full Synthetic with a Wix oil filter.
The factory oil I assume was Subaru 0W-20 (made by Idemitsu)
After the oil change I noticed my oil temperature ran a few degrees cooler. QSFS 5w-30 being thicker should theoretically run slightly warmer?
The outside temperature was the same and even warmer and the QSFS oil just seemed to run cooler in that engine. Oh, the WRX does have a digital oil temperature gauge.
Is it possible that the QSFS reduced friction causes cooler temps?
Again, thanks for all the work you have done. Thought you would be interested in my oil temp observation.
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Hi again,
Yes, I am interested to read about your oil temperature observation. Thanks for sharing.
And yes, traditionally, oil temperatures have typically increased as oil viscosity increases. Because thicker oil flows slower through the engine, and does not cool as well.
0W16, 0W20 and 5W20 are thinner than ideal. And are only intended to possibly, ever so slightly improve gas mileage. Though Owners can never measure any advantage compared to 0W30 or 5W30.
0W30 and 5W30 are “THE IDEAL” viscosity OVERALL for flow, lubrication, cooling, minimizing mechanical engine noise, and for engine wear protection, especially when run aggressively.
In addition to that, the fairly recent API SP revision, especially in the case of 5W30 Quaker State Full Synthetic, API SP, has approached being a Revolutionary change, rather than merely an Evolutionary change.
And yes, its friction reduction formulation reduces heat. Because friction means heat. So, less friction equals less heat.
We are fortunate to have the truly impressive 5W30 Quaker State Full Synthetic, API SP, readily available to us. And we can even get good prices on it at Walmart.
Take care,
540 RAT
540 RAT –
Seeing as how no oil manufacturer is to be trusted in relaying to the public any formulation changes to their oils, do you think it would be prudent to retest the top tier oil/oils in your list every two years or so? I know I would be willing to chip in for the costs and I bet more of your followers would feel the same just for the peace of mind.
Thanks for all you do!
Rich
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Hi Rich,
In a perfect world, that might be something to consider. But, performing my Engineering Torture Test on motor oil, is a huge effort, and takes a lot of time, money aside. So, it simply is not feasible to endlessly test oils.
My Engineering Tests have clearly shown, essentially the only motor oils today that are truly “Top Tier” performing oils, are some of the better, latest API SP oils.
None of the other motor oils even matter. Because the poor performing API SP and non-API motor oils should not be used, if people care about their engines.
We know when API motor oils are reformulated by changes in API certification, such as when they made the significant change from API SN Plus, to API SP.
If they were to change their oils for the worse, they would no longer meet their standing API certification, and could no longer legally be sold showing that standing certification.
With API certified oils in the past, it has been clear that a change was made, be it an API revision, or product name change. That was the case when Castrol ruined their oils. They had name changes and/or API revisions, which is what prompted me to retest them. That’s when I caught them in the act of ruining their oils.
The extremely poor performance of non-API oils such as High Zinc Racing Oils, etc, are really irrelevant, and are not worth retesting. So, we don’t care if they secretly change their formulations.
In the real world, I now typically retest the better performing oils only at API changes, which are significant. That is enough to ensure that we are getting what we need/want.
Take care,
540 RAT
Hi Rat.
(First, I want to ask, do you default see my previous posts on your monitor, or do you have to scroll back, manually?)
So far, I’ve figured out to receive a big box of super fine Amsoil 10W50 DirtBike oil (for a acceptable price), and replaced the timing chain.
But, the Quaker State QSFS for my cars….. No official EU-import company is found, yet. QuakerState.com don’t reply.. I only got in contact with some “local” US sparepart importers, which calculated prices between $49-58 pr. Quart! (NOT a typo) So I’m still searching 😉
During (previously) investigation, I discovered this engine oil tests, in EU:
1.a. Engine oil shear test.
XXX…
1.b. Results of shear tests.
XXX…
I’m all sure, you have some comments to this test…..
And NOT to forget, I’m still both very interested & impressed regarding this fabulous oil blog, THANK YOU!
Take care Sir!
KR.
Carsten.
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Hi again Carsten,
I have to scroll back manually to see your previous posts.
I do not allow links in my Blog. But, I did view both links you sent me, then I deleted them.
I do have a comment about that oil test. A lot of time and effort was obviously spent on that test. And he wants to charge people money to see more of it.
However, it clearly did NOT involve qualified, Degreed Mechanical Engineers. So unfortunately, it is crudely designed and poorly executed, making it just worthless garbage.
If you want to see Accurate and Reliable Engineering Test Data, that has been “PROVEN” TO EXACTLY MATCH real world experience, you still need to come to my Blog. Then look at my “Wear Protection Ranking List”, that you can easily make use of the next time you buy motor oil.
Take care,
540 RAT
Thank you so much Rat!
Surely, I (only) use your results, regarding oil for my water- and aircooled engines, gearbox and differentials.
If I cannot get the QSFS 5W30, chances for the Amsoil Signatures Series are better, but, so far, I’ve only got the 10W30 option, and that is to thick for winter use.
I’ll keep you informed what’s going on “over here”… 😉
Keep safe,
Carsten.